This study was designed to introduce a relevant stimulus at successive time intervals during the entire anesthetic period, including the pre- and postanesthetic periods. Using galvanic skin responses, the authors were able to recognize a plane of light anesthesia and arousal, at which time it is considered that sensory input might be perceived. Presenting to the patient a stimulus of some relevance, but one not likely to be psychically traumatic, they investigated the correlation between the ability to maintain an attention span and to recall in the postoperative period. No recall was obtained during the intraoperative period, the first occurrence of recall being in the immediate postanesthetic period and the incidence of recall increasing with increasing time intervals after the end of anesthesia. The authors conclude, however, that since intraoperative awareness without recall is a possibility, care should be taken to avoid emotionally disturbing auditory stimuli throughout the anesthetic procedure.